Continuity mistake: On the sub, Gregorio and Ingrid are talking to Ingrids parents about the fact they shouldn't be going with them to save Carmen and Juni, and her parents are putting metals flasks down on a side to the left of the grandmother. The flasks are always visible, then the grandparents both activate cool spy gear on themselves, and in this wideshot the flasks vanished.
Revealing mistake: At the scene where all the spy kids are fighting the waiters, watch Gary as he is fighting. The waiter he is fighting throws him back, but then Gary activates his rockets shoes. Yet to activate those shoes you have to tap them together. The rocket shoes activate a few seconds before Gary tapped his heels together.